From a6ca6ae1d7b9933d7ad285ee252463d1e25b46f5 Mon Sep 17 00:00:00 2001
From: carlossanlop <1175054+carlossanlop@users.noreply.github.com>
Date: Tue, 4 Apr 2023 09:57:23 -0600
Subject: [PATCH] Use enumerator to iterate items in the specified enumeration,
 and insert them to the lazily created dictionary if they pass the
 validations.

---
 .../src/System/Formats/Tar/TarHeader.cs              | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/src/libraries/System.Formats.Tar/src/System/Formats/Tar/TarHeader.cs b/src/libraries/System.Formats.Tar/src/System/Formats/Tar/TarHeader.cs
index d576d3c850650..13081f2a75933 100644
--- a/src/libraries/System.Formats.Tar/src/System/Formats/Tar/TarHeader.cs
+++ b/src/libraries/System.Formats.Tar/src/System/Formats/Tar/TarHeader.cs
@@ -113,9 +113,13 @@ internal TarHeader(TarEntryFormat format, TarEntryType typeFlag, TarHeader other
         internal void InitializeExtendedAttributesWithExisting(IEnumerable<KeyValuePair<string, string>> existing)
         {
             Debug.Assert(_ea == null);
-            _ea = new Dictionary<string, string>(existing);
-            foreach (KeyValuePair<string, string> kvp in _ea)
+            Debug.Assert(existing != null);
+
+            using IEnumerator<KeyValuePair<string, string>> enumerator = existing.GetEnumerator();
+            while (enumerator.MoveNext())
             {
+                KeyValuePair<string, string> kvp = enumerator.Current;
+
                 int index = kvp.Key.IndexOfAny(new char[] { '=', '\n' });
                 if (index >= 0)
                 {
@@ -125,6 +129,10 @@ internal void InitializeExtendedAttributesWithExisting(IEnumerable<KeyValuePair<
                 {
                     throw new ArgumentException(SR.Format(SR.TarExtAttrDisallowedValueChar, kvp.Key, "\\n"));
                 }
+
+                _ea ??= new Dictionary<string, string>();
+
+                _ea.Add(kvp.Key, kvp.Value);
             }
         }